Simple template variable usage

🟢 Beginner

template variable

osp-web osp-variables

In this tutorial, the usage of template variables is described. The focus is done to understand the prevalence of usage and all the types of variables available.

• Define a value that references a template via templateId and overrides variables locally.

• Create a first-level template with its own templateVariables.

• Chain a second-level template to provide variables to the root value.

• Understand precedence rules: locally defined variables take priority over those inherited from templates.

git checkout origin/osp-web-configuration .
git checkout origin/osp-variables-configuration .
git checkout origin/example-inheritance-template-value-with-variables .

Steps

1. Create a waveform value constant

root/template/final/owner.waveforms

{
    "moduleId": "modules.waveforms.waveforms-1",
    "waveformConfigurationEntity" : {
        "value": 10,
        "type": "CONSTANT"
    },
    "samplePeriod": {
        "unit": "DAYS",
        "value": 1
    }
}

root/template/final/value.ospp

{
    "name" : "Final value",
    "description": "${description} - ${from-template-of-template}",
    "type": "INTEGER",
    "inputType": "INTEGER",
    "preTransform": "${pre-transform-var}",
    "templateId": "root.template",
    "templateVariables" : {
        "description" : "Description variable",
        "pre-transform-var" : {
            "transform": "add(asInteger(value),1)"
        }
    }
}

• The pre-transform value comes from the value.ospp file (to show the same file templateVariable definition).

• The description uses two variables ${description} which is defined inside the same file

• The from-template-of-template variable which is undefined (will be done in next step)

• A reference is done to root.template via the templateId key

2. Create a first level of template

root/template/template/value.ospp.template

{
    "templateId" : "root.template-of-template",
    "templateVariables" : {
        "from-template-of-template": "This description is overriden"
    }
}

• This value describes a variable which is not used (description), because the variable is defined in the root.final/value.ospp

• A sub-template is defined by the templateVariables key

3. Create a second level of template

root/template/from-template-of-template/value.ospp.template

{
    "templateVariables" : {
        "description": "from-template of template value"
    }
}

• This file declares the variable from-template-of-template. Used by the root.final/value.ospp

4. Add dashboard to visualize the result

This files are used to visualize the example

{
    "configuration": [
      {
        "type": "ValueSubscription",
        "id": "xMkAMwzR",
        "title": "",
        "valueSubscriptions": {
          "values": [
            {
              "id": "root.final",
              "right": "READ_WRITE"
            }
          ]
        }
      }
    ],
    "layout": {
      "lg": [
        {
          "w": 12,
          "h": 5,
          "x": 0,
          "y": 0,
          "i": "xMkAMwzR"
        }
      ]
    },
    "breakpoints": {
      "lg": 1200,
      "md": 996,
      "sm": 768,
      "xs": 480,
      "xxs": 0
    },
    "cols": {
      "lg": 12,
      "md": 10,
      "sm": 6,
      "xs": 4,
      "xxs": 2
    },
    "rowHeight": 150
  }

{
    "moduleId": "modules.web.web-1",
    "title": "Home",
    "description": "OnSphere home",
    "tags": []
}

5. Check result

See the result on the dashboard (hostname:5000), log with default user (user) and password (onsphere)

This schema shows from where each value comes from and the rules.

1. In red, we have a value declared inside a template, but override locally

2. In green, we have the value who override the red value

3. In purple, we have a variable declared in template of template

4. In Orange, we have a node insertion (locally defined)